Heretofore, an n-electrode formed on an n-type layer in a Group III nitride compound semiconductor device such as a blue light-emitting diode has been improved variously to secure ohmic contact between the n-electrode and the n-type layer. An n-electrode introduced in JP-A-11-8410 includes a first electrode material made of at least one member selected from the group consisting of titanium, zirconium and tungsten, a second electrode material made of at least one member selected from the group consisting of aluminum, silicon and germanium, and a third electrode material made of rhodium.
At present, greater improvement in output and efficiency is required of a light-emitting device. From this point of view, there is a demand for greater reduction in resistance between the n-electrode and the n-type layer of a Group III nitride compound semiconductor.
Also when Group III nitride compound semiconductors are applied to other devices than the light-emitting device, resistance between the n-type Group III nitride compound semiconductor and the electrode needs to be sufficiently low. For example, an n-AlGaN/GaN type HFET (Hetero Junction Field Effect Transistor) is noticed as a next-generation power high-frequency device. A low-resistance ohmic contact material exhibiting a sufficiently low contact resistance value in contact with n-AlxGa1-xN (x>0.2) and stable to heat is required for making this device fit for practical use. In the case of a Ti/Al type contact material used for n-GaN at present, the contact resistance value of the contact material increases as the Al content of n-AlGaN increases.